1. Field of the Invention
This invention relates to a method and apparatus for injecting a pulverized fuel, which is generally regarded as being inferior to fluid fuels in combustibility. More particularly, the invention concerns a method and apparatus for injecting such pulverized fuels in an optimum condition, which can improve combustibility while avoiding ash deposition (accumulation on the inner surfaces of the blow pipe), as a result of the improved combustion of the fuel.
This invention also relates to a burner for injecting a pulverized fuel, which is generally regarded as being inferior to fluid fuels in combustibility. More particularly, the invention concerns a burner for injecting such pulverized fuels in an optimum condition, which can improve combustibility while avoiding ash deposition as a result of the improved combustion of the fuel.
2. Description of the Prior Art
As a result of increases in petroleum cost, it has become popular for a blast furnace to rely on an all-coke operation rather than injection of heavy oil.
Research and studies are currently under way on ways to lessen the difficulties of the all-coke operation and to inject a pulverized fuel such as fine coal powder or the like to reduce the consumption of costly coke. However, the pulverized fuel, such as fine coal or the like, (hereinafter referred to generally as "pulverized fuel") has drawbacks in that it has a low combustion rate as compared with heavy oil and contains incombustible components which produce ashes. Therefore, it requires countermeasures in the injecting operation as will be described more particularly hereinbelow.
In a conventional heavy oil injection operation, the tip end of a burner is located in the vicinity of the boundary between a tuyere of a blast furnace and a blow pipe so as to burn the injected fuel completely in a race way immediately downstream of the tuyere. However, if a pulverized fuel is injected at the same position, it will become difficult to burn the pulverized fuel completely within the tuyere and race way, resulting in a lower combustion efficiency.
On the other hand, the pulverized fuels have an ash content, which is fused by the combustion heat and tends to deposit or accumulate on the inner surfaces of the blow pipe upon collision thereagainst, narrowing the blow passage and making it difficult to continue a stable fuel injecting operation. This problem is coupled with the possibility of the ash deposit destabilizing the hot air blowing through the tuyere. The amount of ash deposition or accumulation increases if the injecting position is located in a more upstream position.